1. Field of the Invention
The present invention relates generally to the field of antennas used to receive and transmit light or other forms of electromagnetic energy. More specifically, the present invention relates to optical elements that can be used either to transmit or receive light in a substantially omni-directional pattern, and thereby act as an omni-directional antenna. The invention also can be used as a directional antenna or as an imager over wide fields of view.
2. Statement of the Problem
One of the greatest technical challenges of operating an orbiting spacecraft, such as the shuttle or the proposed space station, is communications with free-flying entities in the proximity of the spacecraft. Conventional radio frequency bands are either congested or unavailable due to prior allocations. A laser communications system is ideal for this application, provided the usual pointing and tracking requirements caused by the tight, collimated output beam can be relaxed. One approach to avoid this problem is to distribute the laser beam over a large volume of space by means of a wide angle lens or a fish-eye lens. Unfortunately, these types of lenses are heavy and cumbersome and, generally are limited to hemispherical coverage, and consequently are not practical for light, mobile transceivers necessary for space or other applications.
A number of devices and processes have been invented in the past relating to optical devices used to convert a collimated or diverging light beam into a near omni-directional pattern, including the following:
______________________________________ Inventor Pat. No. Issue Date ______________________________________ Conover 1,589,370 June 22, 1926 Harrman 1,657,502 Jan. 31, 1928 Osteen, et al. 3,662,165 May 9, 1972 Vandling 3,828,185 Aug. 6, 1974 Britz 3,953,131 Apr. 27, 1976 Koreicho, et al. 4,134,007 Jan. 9, 1979 Maurer 4,161,770 July 17, 1979 Gfeller, et al. 4,214,807 July 29, 1980 Rushworth 4,309,746 Jan. 5, 1982 ______________________________________
Britz discloses an opto-electronic antenna system in which an array of discrete antenna elements 11 are disposed over a hemispherical surface. Each of the antenna elements are connected by light conductors 2 to a beam splitter 3 disposed in the path of a transmitting laser 4 and an optical detector 5. The laser 4 is energized by a signal form the control circuit 6. The output of the laser 4 is transmitted by light conductors 2 to each of the antenna elements 11 for radiation into space. Similarly, radiation which is received by the antenna elements 11 is transmitted by the light conductors 2 through the beam splitter 3 to the detector 5.
Rushworth discloses an electromagnetic radiation diffuser comprising a hollow spherical body 10 having an output window or emission surface 12. The interior surface of the body 10 is coated with a highly reflective diffusion material. The reflective diffusion material serves to transform energy emanating from a source of electromagnetic radiation into a uniform distribution of diffuse radiation within the body 10.
Harrman discloses a headlight having a reflector 7, a hemispherical lens 13, and a concave-convex lens 23. The concave-convex lens 23 has its posterior concavity greater than its anterior convexity so as to deflect rays of light throughout the entire area of the hemispherical lens 13. The lens 13 and reflector 7 combination create a floodlight that is capable of illuminating objects located laterally of the headlight.
Koreicho, et al., disclose a near infrared transmission system for use on an aircraft carrier deck, comprising four optical transmitters or beacons 10, a series of electroluminescent diodes 11, and a parabolic mirror 12. The beam bearing angle from each beacon 10 is approximately 100 degrees. Since the emission from each diode 11 is incoherent, their beams add to each other without interference.
Maurer discloses a guide signal device for use in airport runways, having a prism 1, a housing 2, a reflector 3, and a light source 32.
Osteen discloses an industrial luminaire having a dome-shaped reflector with a number of vertically elongated facets with convex reflecting surfaces to reflect light from the light source downward and outward in overlapping patterns.
The remaining references are noted as being of general interest.
3. Solution to the Problem
None of these prior art references show a compact, lightweight optical device having the structure of the present invention, that is capable of serving as an omni-directional transmit and receive antenna for light or other electromagnetic radiation.